1. Field
The invention relates to improved teat cup inflations used in vacuum operated, automatic milking machines and to methods of forming such inflations.
2. State of the Art
Conventional automatic milking machines utilize teat cup assemblies including a hollow, rigid outer shell or cup having a part which is adapted to be attached to a pulsating vacuum line, and a resilient, tubular liner or inflation extending longitudinally of the shell or cup. The ends of the inflation make sealing engagement with the shell to form an annular vacuum chamber between the shell and the inflation. The pressure in the annular chamber is alternated between subatmospheric pressure and a higher pressure, typically atmospheric, by the pulsating vacuum line attached to the shell. A constant vacuum line is connected to the lower end of the inflation to draw milk from the cow's teat which is received in the upper end of the inflation. The interior of the inflation is, thus, maintained at a constant subatmospheric pressure, and the alternating pressure in the annular chamber periodically forces the walls of the inflation inwardly resulting in a massaging action on the teat as well as collapsing the walls of the inflation below the teat which periodically relieves the teat from exposure to the vacuum in the constant vacuum line.
It is important that the upper portion of the inflation grips the teat firmly to prevent vacuum loss and disengagement of the teat cup from the teat, as well as to prevent the teat cups from moving higher up on the teats during the pulsations of the milking machine, which can ultimately result in constriction of the teat and premature shut off of milk from the udder even though the udder is only partially emptied. The teats of different cows vary considerably in their diameter and length. Changes in teat sizes also occur during the milking. These variations and changes make it very difficult to produce teat cups which can be used in milking a number of cows. In my prior U.S. Pat. No. 3,308,788, there is disclosed a teat cup assembly in which a resilient disk element is mounted on top of the teat cup in position to engage the cow's teat and resiliently retain the cup from falling off the teat. Unfortunately, the teat cup assembly was relatively expensive both to manufacture and to maintain because of the number of individual components in the assembly. In other of my prior art patents, i.e., U.S. Pat. Nos. 3,659,557 and 3,096,740, teat cup assemblies are provided in which the inflation is molded so as to incorporate a diaphragm and an elastic means, respectively, integrally therein. Other inflations which are molded so as to incorporate a resilient retaining element integrally therein are disclosed in U.S. Pat. Nos. 2,744,496; 3,771,494; and 3,973,521. Such molded constructions are again relatively expensive.